Using cloned cDNA probes we have isolated the genomic sequences for the following proteins: alpha skeletal actin, alpha cardiac actin, beta cytoplasmic actin, myosin light chains 1-3, vimentin, pyruvate kinase, and glyceraldehyde phosphate dehydrogenase. These have been defined by DNA sequence analysis. The various actin genes have been subcloned into the eukaryotic vector, PSV2-gpt and transfected into L-cells and into the C2 mouse muscle cell line. Five foot and three foot probes specific for the various chicken actin genes have been used to monitor expression and regulation in these two mouse cell backgrounds. In vivo transcription of the vimentin gene, a single copy gene, produces two distinct mRNA transcripts, both of which are functional and encode the same polypeptide. The mechanism producing these two functional transcripts has been determined. We have compared the nucleotide sequence of the chicken and hamster vimentin genes to determine intronexon junctions, codon usage, and sequence conservation. The myosin light chains 1 and 3 are encoded by a single gene. The organization of the gene has been determined by sequence analysis and contains nine exons. Initiation of transcription of LC1 and LC3 starts at different promotors and processing involves differential splicing. The double adenylation sites are used randomly. The expression of the mouse histone H4 gene is cell cycle regulated. The structure of the gene has been modified to localize the cell-cycle dependent regulatory regions in transfection studies with L-cells using the PSV2-gpt vector system. Pyruvate kinase undergoes an isoform shift during myogenesis. The structure and regulation of the gene is under study. The three unique Acanthamoeba myosin polypeptides have been synthesized in vitro and this assay has been used to isolate the corresponding genomic DNA sequences. Structural comparisons of the genes are underway. Nerve growth factor triggers the differentiation of PC12 neuronal cells in vitro. We have isolated cDNA clones representing those genes that are transcriptionally activated in less than 24 hours after exposure to nerve growth factor. Characterization of the genes is underway.